1. Technical Field
The present invention relates to a method for forming a film pattern and a method for manufacturing an organic EL device, a color filter substrate and a liquid crystal display device.
2. Related Art
In recent years, development of organic electroluminescent devices (hereinafter referred to as “organic EL devices”) having a structure in which a functional layer of a high-performance material is sandwiched between a pair of electrodes has been proceeding. In particular, development of organic EL devices employing an organic light-emitting material as the high-performance material has been proceeding (see, for example, JP-A-11-54270, JP-A-2001-291587, JP-A-2004-31360, and JP-A-2004-127897). In manufacturing such devices, there has been adopted a method of patterning the high-performance material using a droplet discharge method. In this method, a high-performance material, such as an organic fluorescent material or the like, is converted into ink form and the ink (i.e., a functional fluid) is discharged onto a base substrate. Development of methods of drying the ink (i.e., the functional fluid) has also been proceeding (see for example, JP-A-2003-245582, JP-A-2004-311206, and JP-A-2004-330136).
An exemplary method of patterning the high-performance material to form the functional layer on a pixel electrode is as follows: first, forming a partition called a bank around the pixel electrode of ITO or the like formed on the base substrate; then, treating the pixel electrode and a portion of the bank adjacent to the pixel electrode so that they have affinity for liquid and treating the remaining portion of the bank so that it becomes liquid-repellent; and thereafter, discharging ink containing a material for the functional layer onto the pixel electrode and drying the ink. More specifically, there is known a method of forming the functional layer on the pixel electrodes by using a droplet discharge head having a row of nozzles arranged in a sub-scanning direction and discharging ink from the nozzles while causing the droplet discharge head to scan the base substrate in a main scanning direction. Such a method makes it possible to arrange droplets on the order of microns on pixel areas. Therefore, in view of efficiency in use of the material, such a method is more effective than other methods such as spin coating.
However, the partial pressure of solvent molecules, which evaporate from the ink, may become higher in a peripheral portion of a display area (i.e., an effective area) where the pixel electrodes are arranged than in a central portion of the display area. If such a phenomenon occurs, the evaporation rate of the solvent may become extremely high in the peripheral portion of the display area, resulting in unevenness in film thickness of the functional layer or film inclination (i.e., a state in which a film in cross section is tilted) within a pixel in an organic EL device as manufactured. An organic EL device involving such unevenness in film thickness has reduced performance, and if that organic EL device is used as a display device or the like, display unevenness may occur. As such, a technique to solve such a problem is disclosed in JP-A-2002-222695, for example.
JP-A-11-54270 is a first example of related art.
JP-A-2001-291587 is a second example of related art.
JP-A-2004-31360 is a third example of related art.
JP-A-2004-127897 is a fourth example related art.
JP-A-2002-222695 is a fifth example of related art.
JP-A-2003-245582 is a sixth example of related art.
JP-A-2004-311206 is a seventh example of related art.
JP-A-2004-330136 is an eight example of related art.
The technique disclosed in the fifth example of related art is to form a dummy area (i.e., a non-effective area) that does not contribute to display in an area outside the display area and apply to the dummy area the same ink used for the functional layer, thereby reducing variations in the partial pressure of the solvent molecules within the display area. Typically, a bank of the same pattern is formed in both the dummy area and the display area, and the ink is applied to openings of the bank. According to this method, drying of the solvent progresses at an equal rate in both the central and peripheral portions of the display area, making it possible to form high-quality films that do not involve unevenness in film thickness of the functional layer or film inclination.
Because the ink discharged on the dummy area does not form a pixel used for display, a pixel in the dummy area is sometimes called a dummy pixel, as distinguished from a pixel (i.e., an effective pixel) formed in the display area. In order to prevent the above-described unevenness in film thickness, at least several to tens of rows of dummy pixels need be formed. In related art, however, because all dummy pixels are formed with the same pitch and pattern as those of the effective pixels, simply applying the ink to the dummy area in the same manner as to the display area does not always succeed in eliminating the unevenness in film thickness to a sufficient extent. In other words, because drying of the ink discharged on the base substrate progresses from the periphery toward the center concentrically, in the case of a rectangular display area, for example, drying of the solvent sometimes progresses at a higher rate at corner portions of the rectangular display area than at other portions thereof, resulting in failure to avoid the unevenness in film thickness to a sufficient extent.